The LOAD/UNLOAD command allows the host to specify that a tape cartridge present in the drive is either made ready for data transfer (“loaded”) or disabled for data transfer (if Prevent Media Removal is set). It can also cause the cartridge to be ejected from the drive (“unloaded”).
Illegal Field | Reservation | Deferred Error |
Unit Attention | Diagnostic Status | Media Information |
If an unload is to be performed, the drive checks if the tape is currently being loaded. If it is, CHECK CONDITION is reported with a sense key of NOT READY and additional sense of 0401h (becoming ready).
If a load is to be performed, the drive checks to ensure that a tape cartridge is present. If not, it reports CHECK CONDITION with a sense key of NOT READY and additional sense of 3A00h (medium not present). If the media is currently being unloaded or ejected, it reports CHECK CONDITION with sense key of NOT READY and additional sense of 0400h (cause not reportable).
Command descriptor block:
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| 7 | 6 | 5 | 4 |
| 3 | 2 | 1 | 0 |
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| 0 |
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| Operation | Code (1Bh) |
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| Reserved (0) |
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| Immed | |
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| Hold | EOT (0) | ReTen | Load | |
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| 5 |
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| Control |
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CDB fields:
Immed 0 The drive reports status after the command has completed.
| 1 | The drive reports status when it starts the command (after any |
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| prerequisite unloads have completed). |
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Hold | 0 | A normal load/unload will be performed. |
| 1 | A load will cause the cartridge to be pulled in and seated in the drive, but the tape will not |
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| be threaded. |
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| An unload will cause the tape to be unthreaded, but the cartridge will not be ejected. |
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| In Hold position, the Cartridge Memory is accessible. |
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ReTen This field is ignored. | ||
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Load | 0 | The drive performs an unload operation. |
| 1 | The drive performs a load operation. |
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50 Commands